The IPCC First Assessment Report 1990

Overview Preface to the IPCC Overview

The IPCC First Assessment Report consists of this IPCC Overview, •

the Policymaker Summaries of the three IPCC Working Groups (concerned with assessment respectively of the science, impacts and response strategies) and the IPCC Special Committee on the Participation of Developing Countries, and the three reports of the Working Groups.

The Overview brings together material from the four Policymaker Summaries. It presents conclusions, proposes lines of possible action (including suggestions as to the factors which might form the basis for negotiations) and outlines further work which is required for a more complete understanding of the problems of climate change resulting from human activities.

Because the Overview cannot reflect all aspects of the problem which are presented in the three full reports of the Working Groups and the four Policymaker Summaries, it should be read in conjunction with them.

The issues, options and strategies presented in the Report are intended to assist policymakers and future negotiators in their respective tasks. Further consideration of the Report should be given by every government as it cuts across different sectors in all countries. It should be noted that the Report reflects the technical assessment of experts rather than government positions, particularly those governments that could not participate in all Working Groups of IPCC.

51

IPCC Ovei-view would occur under Scenario D towards the end o f the next century. Immediate reductions of over 60% in the net (sources minus sinks) emissions from human a c t i v i t i e s o f l o n g - l i v e d gases w o u l d a c h i e v e s t a b i l i z a t i o n o f c o n c e n t r a t i o n at t o d a y ' s l e v e l s ; methane concentrations w o u l d be stabilized with a 15—20% reduction.

This Overview reflects the conclusions o f the reports o f (i) the three I P C C W o r k i n g Groups on science, impacts, and response strategies, and (ii) the Policymaker Summaries of the I P C C W o r k i n g Groups and the I P C C Special Committee on the Participation o f Developing Countries.

1.

Science •

T h i s section is structured s i m i l a r l y to the P o l i c y m a k e r Summary of W o r k i n g G r o u p I.

1.0.1

We are certain of the following:

•

There is a natural greenhouse effect which already keeps the Earth warmer than it would otherwise be.

•

Emissions resulting from human activities are substan­ tially increasing the atmospheric concentrations of the greenhouse gases: carbon dioxide, methane, chloro­ fluorocarbons (CFCs) and nitrous oxide. These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface. The main greenhouse gas, water vapour, w i l l increase in response to global warming and further enhance it.

1.0.2

1.0.3 •

We calculate with confidence that: Some gases are potentially more effective than others at changing climate, and their relative effectiveness can be estimated. Carbon dioxide has been responsible for over half o f the enhanced greenhouse effect in the past, and is likely to remain so in the future.

Atmospheric concentrations o f the long-lived gases (carbon dioxide, nitrous oxide and the C F C s ) adjust only s l o w l y to changes o f emissions. C o n t i n u e d emissions of these gases at present rates would commit us to increased concentrations for centuries ahead.

The longer emissions continue to increase at presentday rates, the greater reductions would have to be for concentrations to stabilize at a given level.

•

The human-caused emissions o f carbon dioxide are much smaller than the natural exchange rates of carbon dioxide between the atmosphere and the oceans, and between the atmosphere and the terrestrial system.

The natural exchange rates were, however, in close balance before human-induced emissions began; the steady anthropogenic emissions into the atmosphere represent a significant disturbance o f the natural carbon cycle.

Based on current model results, we predict: A n average rate o f increase o f g l o b a l m e a n temperature during the next century o f about 0.3°C per decade (with an uncertainty range o f 0 . 2 — 0 . 5 ° C per decade) assuming the I P C C Scenario A (Business-asUsual) emissions o f greenhouse gases; this is a more rapid increase than seen over the past 10,000 years.

This w i l l result in a likely increase in the global mean temperature o f about 1°C above the present value by 2025 (about 2 ° C above that i n the p r e - i n d u s t r i a l period), and 3 ° C above today's value before the end o f the next century (about 4 ° C above pre-industrial). The rise w i l l not be steady because of other factors.

U n d e r the other I P C C emissions scenarios w h i c h assume progressively increasing levels o f controls, rates o f increase in global mean temperature o f about 0 . 2 ° C per decade (Scenario B ) , just above 0 . 1 ° C per decade (Scenario C ) and about О . Г С per decade (Scenario D ) . The rise w i l l not be steady because o f other factors.

Land surfaces warm more rapidly than the oceans, and higher northern latitudes warm more than the global mean in winter.

For the four scenarios o f future emissions which I P C C has developed as assumptions (ranging from one where few or no steps are taken to limit emissions, viz..

Scenario A or Business-as-Usual Scenario, through others with increasing levels of controls respectively called Scenarios B , С and D ) . there w i l l be a doubling of equivalent carbon dioxide concentrations from preindustrial levels by about 2025, 2040 and 2050 in Scenarios A , B , and С respectively (see the section " W h i c h gases are the most i m p o r t a n t ? " in the P o l i c y m a k e r S u m m a r y o f W o r k i n g G r o u p I for a d e s c r i p t i o n o f the c o n c e p t o f e q u i v a l e n t c a r b o n dioxide). See the Appendix for a description of the I P C C emissions scenarios.

•

The oceans act as a heat sink and thus delay the full effect o f a greenhouse warming. Therefore, we would be committed to a further temperature rise w h i c h would progressively become apparent in the ensuing decades and c e n t u r i e s . M o d e l s p r e d i c t that as greenhouse gases increase, the realized temperature rise at any given time is between 50 and 80% o f the committed temperature rise.

U n d e r the I P C C S c e n a r i o A ( B u s i n e s s - a s - U s u a l ) emissions, an average rate o f global mean sea-level

•

dioxide

rise of about 6 c m per decade over the next century

concentrations at about twice the pre-industrial level

(with an uncertainty range o f 3—10 c m per decade).

Stabilization

of

equivalent

carbon

52

IPCC Overview mainly due to themial expansion of the oceans and the melting of some land ice. The predicted rise is about 20 c m in global mean sea level by 2030, and 65 c m by the end o f the next century. There w i l l be significant regional variations.

1.0.4

response (feedback) processes are poorly understood, it appears that, as climate warms, these feedbacks w i l l lead to an overall increase, rather than a decrease, in natural greenhouse gas abundances. For this reason, climate change is likely to be greater than the estimates given above.

With regard to uncertainties, we note that: 2.

There are many uncertainties in o u r p r e d i c t i o n s particularly with regard to the timing, magnitude and regional pattems of climate change, especially changes in precipitation.

2.0.1 The report on impacts o f W o r k i n g G r o u p II is based on the w o r k o f a n u m b e r o f s u b g r o u p s , u s i n g independent studies w h i c h have used d i f f e r e n t methodologies. Based on the existing literature, the studies have used several scenarios to assess the potential impacts of climate change. These have the features of:

These uncertainties are due to our incomplete understanding o f sources and sinks o f greenhouse gases and the responses of clouds, oceans and polar ice sheets to a change o f the radiative forcing caused by increasing greenhouse gas concentrations.

These processes are already partially understood, and we are confident that the uncertainties can be reduced by further research. However, the complexity of the system means that we cannot rule out s u ф r i s e s .

1.0.5

Impacts

i)

an effective d o u b l i n g o f C O 2 i n the between now and 2025 to 2050;

ii)

a consequent increase o f global mean temperature in the range o f 1.5°C to 4 . 5 ° C ;

iii)

an unequal global distribution of this temperature increase, namely a smaller increase of half the global mean in the tropical regions and a larger increase o f twice the global mean in the polar regions;

iv)

a sea-level rise of about 0.3—0.5 m by 2050 and about 1 m by 2100, together with a rise in the temperature o f the surface ocean layer o f between 0.2° and 2 . 5 ° C .

Our judgement is that: G l o b a l mean surface air temperature has increased by 0.3 to 0 . 6 ° C over the last 100 years, with the five global-average warmest years being in the 1980's.

Over the same period global sea-level increased by 10 to 20 c m . These increases have not been smooth in time, nor uniform over the globe.

atmosphere

2.0.2 These scenarios pre-date, but are in line with, the assessment o f W o r k i n g G r o u p I w h i c h , for Scenario A (Business-as-Usual) has estimated the magnitude of sealevel rise at about 20 cm by 2030 and about 65 cm by the end of the next century. W o r k i n g Group I has also predicted the increase in global mean temperatures to be about 1°C above the present value by 2025 and 3 ° C before the end o f the next century.

The size o f the w a r m i n g over the last century is broadly consistent with the prediction by climate models, but is also of the same magnitude as natural climate variability. If the sole cause o f the observed warming were the human-made greenhouse effect, then the implied climate sensitivity would be near the lower end of the range inferred from models. Thus the observed increase could be largely due to this natural variability: altematively this variability and other human factors could have offset a still larger humani n d u c e d greenhouse w a r m i n g . T h e u n e q u i v o c a l detection o f the enhanced greenhouse effect from observations is not likely for a decade or more.

2.0.3 A n y predicted effects o f climate change must be v i e w e d i n the c o n t e x t o f o u r present d y n a m i c a n d changing w o r l d . Large-scale natural events such as E l N i n o can cause significant impacts on agriculture and human settlement. The predicted population e x p l o s i o n w i l l p r o d u c e severe i m p a c t s on l a n d use and on the demands for energy, fresh water, food and housing, which w i l l vary from region to region a c c o r d i n g to national incomes and rates o f development. In many cases, the impacts w i l l be felt most severely in regions already under stress, mainly the developing countries. Human-induced climate change due to continued uncontrolled emissions w i l l accentuate these i m p a c t s . F o r instance, c l i m a t e change, pollution and ultraviolet-B radiation from ozone depletion can interact, reinforcing their damaging effects on materials and organisms. Increases in atmospheric c o n c e n t r a t i o n s o f g r e e n h o u s e gases m a y l e a d to i r r e v e r s i b l e c h a n g e i n the c l i m a t e w h i c h c o u l d be detectable by the end of this century.

Measurements from ice cores going back 160,000 years show that the Earth's temperature closely paralleled the amount o f carbon d i o x i d e and methane in the atmosphere. Although we do not know the details o f cause and effect, calculations indicate that changes in these greenhouse gases were part, but not a l l , o f the reasons for the large ( 5 — 7 ° C ) global temperature swings between ice ages and interglacial periods.

Natural sources and sinks o f greenhouse gases are sensitive to a change in climate. Although many of the 53

IPCC Overview 2.0.4 C o m p r e h e n s i v e estimates o f the p h y s i c a l and biological effects o f climate change at the regional level are difficult. Confidence in regional estimates of critical climatic factors is low. This is particularly true o f precipitation and soil moisture, where there is considerable disagreement between various general circulation model and palaeoanalogue results. M o r e o v e r , there are several scientific uncertainties regarding the relationship between climate change and biological effects and between these effects and socioeconomic consequences.

Sahel R e g i o n o f A f r i c a . Southeast A s i a , and the A s i a n region o f the U S S R and China. There is a possibility that potential productivity of high and mid latitudes may increase because o f a prolonged growing season, but it is not likely to open up large new areas for production and it w i l l be mainly confined to the Northem Hemisphere.

2.1.2 Pattems of agricultural trade could be altered by decreased cereal production in some of the currently highproduction areas, such as westem Europe, southem U S A , parts o f South A m e n c a and westem Australia. Horticultural production in mid-latitude regions may be reduced. O n the other hand, cereal production could increase in northem Europe. Policy responses directed to breeding new plant cultivars, and agricultural management designed to cope with changed climate conditions, could lessen the severity of regional impacts. O n the balance, the evidence suggests that in the face o f estimated changes o f c l i m a t e , food p r o d u c t i o n at the g l o b a l l e v e l can be m a i n t a i n e d at essentially the same level as would have occurred without climate change; however, the cost o f a c h i e v i n g this is unclear. Nonetheless, c l i m a t e change may intensify difficulties in coping with rapid population growth. A n increase or change in U V - B radiation at ground level resulting from the depletion of stratospheric ozone will have a negative impact on crops and livestock.

2.0.5 This impact study pan o f the Overview does not attempt to a n t i c i p a t e any a d a p t a t i o n , t e c h n o l o g i c a l innovation or any other measures to diminish the adverse effects o f climate change that w i l l take place in the same time frame. T h i s is e s p e c i a l l y important for h e a v i l y managed sectors, eg, agnculture, forestry and public health.

2.0.6 Finally, the issue o f timing and rates of change need to be considered; there w i l l be lags between: i)

e m i s s i o n s o f greenhouse gases and d o u b l i n g o f concentrations:

ii)

doubling of greenhouse gas concentrations and change in climate;

iii)

c h a n g e s i n c l i m a t e and resultant p h y s i c a l and

2.1.3 The rotation period o f forests is long and current forests will mature and decline dunng a climate in which they are increasingly more pooriy adapted. Actual impacts depend on the physiological adaptability o f trees and the hostparasite relationship. Large losses from both factors in the form o f forest declines can occur. Losses from wildfire w i l l be increasingly extensive. The climate zones which control species distnbution will move poleward and to higher elevations. Managed forests require large inputs in terms of choice of seedlot and spacing, thinning and protection. They provide a variety of products from fuel to food.

biological effects; and iv)

changes in physical and ecological effects and resultant socioeconomic (including ecological) consequences.

The shorter the lags, the less the ability to cope and the greater the socioeconomic impacts.

2.0.7 There is uncertainty related to these time lags.

The changes w i l l not be steady and s u Ń„ r i s e s cannot be ruled out. The severity o f the impacts w i l l depend to a large degree on the rate o f climate change.

2.1.4 T h e degree o f dependency on products varies among countries, as does the ability to cope with and to withstand loss. The most sensitive areas w i l l be where species are close to their b i o l o g i c a l limits in terms o f temperature and moisture. This is likely to be, for example, in s e m i - a r i d areas. S o c i a l stresses can be expected to increase and consequent anthropogenic damage to forests may occur. These increased and non-sustainable uses w i l l place m o r e pressure o n forest i n v e s t m e n t s , forest conservation and sound forest management.

2.0.8 Despite these uncertainties. W o r k i n g Group II has been able to reach some major c o n c l u s i o n s . These are presented below.

2.1

Agriculture and forestry

2.1.1 Sufficient evidence is now available from a variety of different studies to indicate that changes of climate would have an important effect on agriculture and livestock.

Studies have not yet conclusively determined whether, on average, g l o b a l a g r i c u l t u r a l potential w i l l increase or decrease. Negative impacts could be felt at the regional level as a result of changes in weather and pests associated with climate change, and changes in ground-level ozone associated with pollutants, necessitating innovations in technology and agricultural management practices. There may be severe effects in some regions, particularly decline in production in regions o f high present-day vulnerability that are least able to adjust. These include B r a z i l , Peru, the

2.2

Natural terrestrial ecosystems

2.2.1 N a t u r a l terrestrial e c o s y s t e m s c o u l d face significant consequences as a result o f the global increases in the atmospheric concentrations o f greenhouse gases and the associated c l i m a t i c changes. Projected changes in temperature and precipitation suggest that climatic zones could shift several hundred kilometres towards the poles over the next fifty years. Flora and fauna would lag behind

54

IPCC Overview dependent on unregulated river systems, are particularly vulnerable to hydrometeorological change. O n the other hand, regions such as the westem U S S R and western United States that have large regulated water resource systems are less sensitive to the range of hydrometeorological changes in the assumed scenario. In addition to changes in water supply, water demand may also change through human efforts to conserve, and through improved growth efficiency of plants in a higher C O 2 environment. Net socioeconomic consequences must consider both supply and demand for water. Future design in water resource engineering w i l l need to take possible impacts into account when considering structures with a life span to the end of the next century.

Where precipitation increases, water management practices, such as urban storm drainage s y s t e m s , m a y require upgrading in capacity. Change in drought risk represents potentially the most serious impact o f climate change on agriculture at both regional and global levels.

these climatic shifts, suiA/iving in their present location and. therefore, c o u l d find themselves m a different climatic regime. These regimes may be more or less hospitable and, therefore, could increase productivity for some species and decrease that of others. Ecosystems are not expected to move as a single unit, but would have a new structure as a consequence of alterations in distribution and abundance of species.

2.2.2 The rate of projected climate changes is the major factor determining the type and degree o f climatic impacts on natural terrestrial ecosystems. These rates are likely to be faster than the ability o f some species to respond and responses may be sudden or gradual.

2.2.3 Some species could be lost o w i n g to increased stress leading to a reduction of global biological diversity.

Increased incidence o f disturbances such as pest outbreaks and fire are likely to occur in some areas and these could enhance projected ecosystem changes.

2.4

2.2.4 Consequences o f C O 2 enrichment and climate change for natural terrestrial ecosystems could be modified by other environmental factors, both natural and maninduced (e.g. by air pollution).

2.4.1 The most vulnerable human settlements are those especially exposed to natural hazards, e g coastal or river flooding, severe drought, landslides, severe wind storms and tropical cyclones. The most vulnerable populations are in d e v e l o p i n g countries, in the l o w e r - i n c o m e groups: residents o f coastal lowlands and islands, populations in s e m i - a r i d grasslands, and the urban p o o r in squatter settlements, s l u m s and shanty t o w n s , e s p e c i a l l y in megacities. In coastal lowlands such as in Bangladesh.

C h i n a and E g y p t , as w e l l as in s m a l l island nations, inundation due to sea-level rise and storm surges could lead to significant movements of people. Major health impacts are possible, especially in large urban areas, o w i n g to changes in availability o f water and food and increased health problems due to heat stress spreading o f infections.

Changes in precipitation and temperature could radically alter the patterns o f vector-borne and viral diseases by s h i f t i n g them to h i g h e r l a t i t u d e s , thus p u t t i n g large populations at risk. A s similar events have in the past, these changes could initiate large migrations of people, leading over a number of years to severe disruptions of settlement pattems and social instability in some areas.

2.2.5 Most at risk are those communities in which the options for adaptability are limited (e.g. montane, alpine, polar, island and coastal communities, remnant vegetation, and heritage sites and reserves) and those communities where c l i m a t i c changes add to e x i s t i n g stresses. T h e s o c i o e c o n o m i c consequences o f these impacts w i l l be significant, especially for those regions of the globe where societies and related economies are dependent on natural terrestrial ecosystems for their welfare. Changes in the availability of food, fuel, medicine, construction material and income are possible as these ecosystems are changed.

Important fibre products could also be affected in some regions.

2.3

Human settlements, energy, transport, and industrial sectors, human health and air quality

Hydrology and water resources

2.3.1 Relatively small climate changes can cause large water resource problems in many areas, especially arid and semi-arid regions and those humid areas where demand or pollution has led to water scarcity. Little is known about regional details o f greenhouse-gas-induced hydrometeorological change. It appears that many areas w i l l have increased precipitation, soil moisture and water storage, thus altering pattems o f agricultural, ecosystem and other water use. Water availability w i l l decrease in other areas, a most important factor for already marginal situations, such as the S a h e l i a n zone in A f r i c a . T h i s has s i g n i f i c a n t

2.4.2 G l o b a l w a r m i n g can be expected to affect the availability o f water resources and biomass, both major sources of energy in many developing countries. These effects are likely to differ between and within regions with some areas losing and others gaining water and biomass.

Such changes in areas which lose water may jeopardize energy supply and materials essential for human habitation and energy. Moreover, climate change itself is also likely to have different effects between regions on the availability o f other forms of renewable energy such as wind and solar power. In developed countries some of the greatest impacts on the energy, transport and industrial sectors may be determined by policy responses to climate change such as

i m p l i c a t i o n s for a g r i c u l t u r e , for water storage and distribution, and for generation o f hydroelectric power. In some limited areas, for example, under an assumed scenario of a Г С to 2°C temperature increase, coupled with a 10% reduction in precipitation, a 4 0 — 7 0 % reduction in annual mnoff could occur. Regions such as southem A s i a , that are 55

IPCC Overview fuel regulations, emission fees or policies promoting greater use o f mass transit. In developing countnes, climate-related changes in the availability and price of production resources such as energy, water, food and fibre m a y affect the competitive position o f many industries.

particulariy at m i d latitudes, with some regions at high latitudes possibly experiencing increases in seasonal snow cover. Changes in the volume o f snow cover, or the length of the snow c o v e r season, w i l l have both positive and negative impacts on regional water resources (as a result o f changes in the v o l u m e and the t i m i n g o f runoff from snowmelt), on regional transportation (road, marine, air and rail), and on recreation sectors.

2.4.3 Global wanming and increased ultraviolet radiation resulting from depletion of stratospheric ozone may produce adverse impacts on air quality such as increases in groundlevel ozone in some polluted urban areas. A n increase o f ultraviolet-B radiation intensity at the Earth's surface would increase the risk o f damage to the eye and skin and may disrupt the marine food chain.

2.5

2.6.3 Globally, the ice contained in glaciers and ice sheets is projected to decrease, with regional responses complicated by the effect of increased snowfall in some areas which could lead to accumulation of ice. G l a c i a l recession w i l l have significant implications for local and regional water resources, and thus impact on water availability and on hydroelectric power potential. Glacial recession and loss of ice from ice sheets w i l l also contribute to sea-level rise. Permafrost, which currently underiies 20—25% o f the land mass of the Northern Hemisphere, could experience significant degradation within the next 40—50 years. Projected increases in the thickness of the freeze-thaw (active) layer above the

Oceans and coastal zones

2.5.1 G l o b a l w a r m i n g w i l l accelerate sea-level rise, modify ocean circulation and change marine ecosystems, with considerable socioeconomic consequences. These effects will be added to present trends o f rising sea-level, and other effects that have already stressed coastal resources, such as

permafrost and a recession of permafrost to higher latitudes and altitudes could lead to increases in terrain instability, erosion and landslides in those areas which currently contain permafrost. A s a result, overiying ecosystems could be significantly altered and the integrity of man-made structures and facilities reduced, thereby influencing existing human settlements and development opportunities.

pollution and over-harvesting. A 30—50 c m sea-level rise (projected by 2050) w i l l threaten low islands and coastal zones. A 1 m rise by 2100 would render some island countries uninhabitable, displace tens o f millions of people, seriously threaten l o w - l y i n g urban areas, flood productive land, contaminate fresh water supplies and change coastlines. A l l of these impacts would be exacerbated if droughts and storms become more severe. Coastal protection would involve very significant costs. Rapid sea-level rise would change coastal ecology and threaten many important fisheries. Reductions in sea ice w i l l benefit shipping, but seriously impact on icedependent marine mammals and birds.

3.

3.0.1 T h e consideration o f climate change response strategies presents formidable difficulties for policymakers.

The information available to make sound policy analyses is inadequate because of:

2.5.2 Impacts on the global oceans w i l l include changes in the heat balance, shifts in ocean circulation which w i l l affect the capacity of the ocean to absorb heat and C O , and changes in u p w e l l i n g zones associated with fisheries.

Effects w i l l vary by geographic zones, with changes in habitats, a decrease in biological diversity and shifts in m a r i n e o r g a n i s m s and p r o d u c t i v e z o n e s , i n c l u d i n g commercially important species. Such regional shifts in fisheries w i l l have major socioeconomic impacts.

2.6

Response strategies

Seasonal snow cover, ice and permafrost

(a)

uncertainty with respect to how effective specific response options or groups o f options would be in actually averting potential climate change;

(b)

uncertainty w i t h respect to the costs, effects on e c o n o m i c g r o w t h , and other e c o n o m i c and social implications of specific response options or groups o f options.

3.0.2

T h e I P C C r e c o m m e n d s a p r o g r a m m e for the

development and implementation o f global, comprehensive and phased action for the resolution o f the global warming

2.6.1 The global areal extent and volume of elements o f the terrestrial cryosphere (seasonal snow cover, near-surface layers o f permafrost and some masses o f ice) w i l l be substantially reduced. These reductions, when reflected r e g i o n a l l y c o u l d have s i g n i f i c a n t i m p a c t s o n related e c o s y s t e m s and s o c i a l and e c o n o m i c a c t i v i t i e s .

Compounding these impacts in some regions is that, as a result o f the as.sociated climatic warming positive feedbacks, the reductions could be sudden rather than gradual.

problem under a flexible and progressive approach.

•

A major dilemma of the issue o f climate change due to increasing emission o f greenhouse gases in the atmosphere is that actions may be required well before many o f the specific issues that are and w i l l be raised can be analyzed more thoroughly by further research.

The

2.6.2

C F C s are b e i n g phased out to protect

stratospheric ozone layer.

T h e areal coverage o f seasonal snow and its

the

T h i s a c t i o n w i l l also

effectively slow down the rate o f increase o f radiative

d u r a t i o n are p r o j e c t e d to decrease in most r e g i o n s .

56

IPCC Overview forcing of greenhouse gases in the atmosphere. Every effort should be made to find replacements that have little or no greenhouse warming potential or ozone depletion potefitial rather than the H C F C s and H F C s that are now being considered.

environmental protection as the basis for continued economic growth. Environmental considerations must be s y s t e m a t i c a l l y integrated into a l l p l a n s for d e v e l o p m e n t . T h e right balance must be struck between e c o n o m i c g r o w t h and e n v i r o n m e n t a l objectives.

The single largest anthropogenic source o f radiative forcing is energy production and use. The energy sector a c c o u n t s for an e s t i m a t e d 4 6 % ( w i t h an uncertainty range o f 3 8 — 5 4 % ) o f the enhanced radiative forcing resulting from human activities.

Emissions from developing countries are growing in order to meet their development requirements and thus, over time, are likely to represent an increasingly significant percentage o f global emissions. A s the greenhouse gas emissions in developing countries are increasing with their population and economic growth, rapid transfer, on a preferential basis, to developing countries, o f technologies which help to monitor, limit or adapt to climate change, without hindering their e c o n o m i c development, is an urgent requirement.

Developing countries should, within the limits feasible, take measures to suitably adapt their economies.

R e c o g n i z i n g the poverty that prevails among the populations o f developing countries, it is natural that achieving economic growth is given priority by them.

N a r r o w i n g the gap between the industrialized and developing world w o u l d provide a basis for a full partnership o f all nations in the world and would assist d e v e l o p i n g countries in d e a l i n g with the climate change issue.

It is n o t e d that e m i s s i o n s due to f o s s i l f u e l combustion amount to about 7 0 — 9 0 % o f the total a n t h r o p o g e n i c e m i s s i o n s o f C O 2 i n t o the atmosphere, whereas the remaining 10—30% is due to human use o f terrestrial ecosystems. A major decrease o f the rate of deforestation as well as an increase in afforestation w o u l d contribute s i g n i f i c a n t l y to s l o w i n g the rate o f C O 2 concentrations increase in the atmosphere; but it would be well below that required to stop it. This underlines that when forestry measures have been i n t r o d u c e d , o t h e r m e a s u r e s to l i m i t or r e d u c e greenhouse emissions should not be neglected.

3.1 •

Roles of industrialized and developing countries 3.2

I n d u s t r i a l i z e d and d e v e l o p i n g c o u n t r i e s have a common but varied responsibility in dealing with the problem o f climate change and its adverse effects.

The former should take the lead in two ways:

The climate scenario studies of W o r k i n g Groups I and III outline control policies on emissions that would slow global warming from the presently predicted value of about 0.3°C per decade to about 0.1 °C per decade (see Appendix).

i) A major part o f emissions affecting the atmos p h e r e at p r e s e n t o r i g i n a t e s i n i n d u s t r i a l i z e d countries where the scope for change is greatest.

I n d u s t r i a l i z e d c o u n t r i e s s h o u l d adopt d o m e s t i c measures to limit climate change by adapting their own economies in line with future agreements to limit emissions.

The potentially serious consequences o f c l i m a t e change give sufficient reasons to begin adopring response strategies that can be justified immediately even i n the face o f significant uncertainties. T h e response strategies include:

ii) T o co-operate w i t h d e v e l o p i n g c o u n t r i e s in intemational action, without standing in the way o f the latter"s development by contributing additional f i n a n c i a l r e s o u r c e s , by a p p r o p r i a t e transfer o f technology, by engaging in close co-operation in scientific observation, analysis and research, and finally by means of technical co-operation geared to forestalling and managing environmental problems.

•

Options

p h a s i n g out o f C F C e m i s s i o n s and c a r e f u l assessment o f the greenhouse gas potential of proposed substitutes; e f f i c i e n c y improvements and c o n s e r v a t i o n in energy supply, conversion and end use, in particular through i m p r o v i n g d i f f u s i o n o f energy-efficient t e c h n o l o g i e s , i m p r o v i n g the e f f i c i e n c y o f massproduced goods, reviewing energy-related price and tariff systems to better reflect environmental costs;

Sustainable development' in industrialized as well as d e v e l o p i n g countries requires proper concern for

' Sustainable development is developmeni that meets the needs of the present without compromising the ability of future generations to meet their own needs and does not imply in any way encroachment upon national sovereignty. (Annex II to decision 15/2 of the 15th session of the U N E P Governing Council. Nairobi, May 1989

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sustainable forest management and afforestation;

-

use o f cleaner, more efficient energy sources with

lower or no emissions o f greenhouse gases; 57

review of agriculture practices.

IPCC Overview -

There is no single quick-fix technological option for l i m i t i n g greenhouse gas e m i s s i o n s . Phased and flexible response strategies should be designed to enhance relevant technological research, development and deployment, including i m p r o v e m e n t and r e a s s e s s m e n t o f e x i s t i n g technologies. Such strategies should i n v o l v e o p p o r t u n i t i e s for i n t e r n a t i o n a l c o - o p e r a t i o n . A comprehensive strategy addressing all aspects of the problem and reflecting environmental, economic and social costs and benefits is necessary.

reflecting obligations o f both industrialized and developing countries in addressing this issue, while recognizing the special needs o f developing countries, in particular in the areas o f financing and technology.

3.2.1 The degree to which options are viable w i l l also vary considerably depending on the region or country involved. For each country, the implications o f specific options w i l l depend on its s o c i a l , e n v i r o n m e n t a l and economic context. O n l y through careful analysis o f all available options w i l l it be possible to determine which are best suited to the circumstances of a particular country or region. Initially, the highest priority should be to review existing policies with a view to minimizing conflicts with the goals of climate change strategies. N e w policies w i l l be required.

Because a large, projected increase m world population w i l l be a major factor in causing the projected increase in global greenhouse gases, it is essential that global climate change strategies take into account the need to deal with the issue of the rate of growth o f the world population.

Subject to their particular circumstances, individual nations, or groups o f nations, may wish to consider taking steps now to attempt to limit, stabilize or reduce the e m i s s i o n o f greenhouse gases resulting from human activities and prevent the destruction and improve the effectiveness of sinks. One option that governments may wish to consider is the setting o f targets for C O j and other greenhouse gases.

In the long-term perspective, work should begin on defining criteria for selection o f appropriate options which would reflect the impacts of climate change and Its costs and benefits on the one hand, and social and economic costs and benefits of the options on the other.

Consideration of measures for reducing the impacts of g l o b a l c l i m a t e c h a n g e s h o u l d b e g i n as s o o n as p o s s i b l e , p a r t i c u l a r l y w i t h regard to disaster preparedness policies, coastal zone management and control measures for desertification, many o f these being justified in their own right. Measures to limit or adapt to climate change should be as cost-effective as possible while taking into account important social implications. L i m i t a t i o n and adaptation should be considered as an integrated package.

A large number of options were preliminarily assessed

by I P C C W o r k i n g G r o u p III. It appears that some o f these options may be economically and socially feasible for implementation i n the near-term w h i l e others, because they are not yet technically or economically viable, may be more appropriate for implementation in the longer term. In general, the W o r k i n g Group found that the most effective response strategies, especially in the short term, are those which are: • beneficial for reasons other than climate change and j u s t i f i a b l e in their o w n r i g h t , for e x a m p l e increased energy efficiency and lower greenhouse gas emission technologies, better management o f forests, and other natural r e s o u r c e s , and r e d u c t i o n s i n e m i s s i o n s o f C F C s and other o z o n e d e p l e t i n g substances that are also radiatively important gases;

able to serve m u l t i p l e s o c i a l , e c o n o m i c and environmental p u Ń„ o s e s ; flexible

A s s e s s i n g areas at r i s k f r o m s e a - l e v e l rise and d e v e l o p i n g c o m p r e h e n s i v e management plans to reduce future vulnerability o f populations and coastal developments and ecosystems as part o f coastal zone management plans should begin as soon as possible.

E n v i r o n m e n t a l objectives can be pursued through regulations and/or through market-based economic instruments. The latter, through their encouragement of flexible selection o f abatement measures, tend to e n c o u r a g e i n n o v a t i o n and the d e v e l o p m e n t o f improved technologies and practices for reducing emissions and therefore frequently offer the possibility of achieving environmental improvements at lower costs than through regulatory mechanisms. It is not likely, however, that economic instruments w i l l be applicable to all circumstances.

e c o n o m i c a l l y e f f i c i e n t and cost e f f e c t i v e , in particular those that use market-based mechanisms;

-

administratively practical and effective in terms o f

application, monitoring and enforcement;

and phased, so that they can be easily

modified to respond to increased understanding o f scientific, t e c h n o l o g i c a l and e c o n o m i c aspects o f

Three factors are considered as potential barriers to the

climate change;

operation o f markets and/or the a c h i e v e m e n t o f -

compatible with economic growth and the concept

environmental objectives through market mechanisms.

of sustainable development;

These are:

58

IPCC Overview

4.

i) information problems, w h i c h can often cause markets to produce less effective or unfavourable environmental outcomes;

4.0.1 It IS o b v i o u s that the i m p a c t o n a n d the participation by the developing countries in the further development of a future strategy is essential. The I P C C has attempted to address this specific issue by establishing a Special Committee on the Participation of Developing Countries and requested it to identify factors inhibiting the full participation of the developing countries in I P C C and recommend remedial measures where possible. The C o m m i t t e e stressed that full participation includes not o n l y the p h y s i c a l presence at m e e t i n g s but a l s o the development o f national competence to address all issues of concem such as the appreciation o f the scientific basis of climate change, the potential impacts on society o f such change and evaluations o f practical response strategies for national/regional applications.

ii) e x i s t i n g measures and institutions, w h i c h can encourage individuals to behave in environmentally damaging ways; and iii) b a l a n c i n g

competing

objectives

(social,

environmental and economic).

3.2.2 A n initial response strategy may therefore be to address information problems directly and to review existing measures which may be barriers. For example, prior to possible adoption of a system of emission charges, countries should examine existing subsidies and tax incentives on energy and other relevant greenhouse gas producing sectors. •

Participation of developing countries

With respect to institutional mechanisms for providing financial co-operation and assistance to developing countries, a two track approach was considered:

4.0.2 The factors that kept developing countries from fully participating were identified by the Special Committee as:

i) one track built on work underway or planned in existing institutions. Bilateral donors could further integrate and reinforce the environmental components o f their assistance p r o g r a m m e s and d e v e l o p cofinancing arrangements with multilateral institutions while ensuring that this does not impose inappropriate environmental conditions; ii) p a r a l l e l to this track the p o s s i b i l i t y o f new mechanisms and facilities was considered. S o m e developing and industrialized countries suggested that new mechanisms directly related to a future climate convention and protocols that might be agreed upon, such as a new intemational fund, were required.

-

insufficient information;

-

insufficient communication;

-

limited human resources;

-

institutional difficulties;

-

limited financial resources.

4.0.3 O n some o f these factors, the I P C C W o r k i n g Groups have developed p o l i c y options w h i c h are to be found in their respective reports.

Govemments should undertake now:

D e v e l o p i n g c o u n t r i e s w i l l , i n some cases, need additional financial resources for supporting their efforts to promote activities which contribute both to limiting greenhouse gas emissions and/or adapting to the adverse effects o f climate change, while at the same time promote economic development. Areas of co-operation could include, inter alia:

accelerated and co-ordinated research programmes to reduce scientific and socioeconomic uncertainties with a view towards improving the basis for response strategies and measures; review of planning in the fields of energy, industry, transportation, urban areas, coastal zones and resource use and management; encouragement o f b e n e f i c i a l b e h a v i o r a l and structural (e.g. t r a n s p o r t a t i o n and h o u s i n g infrastructure) changes;

efficient use o f energy resources, the use o f f o s s i l fuels w i t h l o w e r greenhouse gas e m i s s i o n rates or non-fossil sources, the development o f clean and renewable energy sources, such as: biomass, wind-power, wave-power, hydroelectric and solar, wherever applicable;

-

-

e x p a n s i o n o f the g l o b a l ocean o b s e r v i n g and

monitoring systems.

increased rational utilization of forest products,

sound forest management practices and agricultural techniques w h i c h reduce the negative effects on

3.2.3 It should be noted that no detailed assessments have been made as of yet of the economic costs and benefits, t e c h n o l o g i c a l f e a s i b i l i t y or m a r k e t p o t e n t i a l o f the underlying policy assumptions.

climate; facilitating the development and transfer o f clean and safe technologies in areas which could include: 59

IPCC Overview +

the building and manufacturing industries;

+

public transport systems;

+

industry;

5.

The measures noted above require a high degree o f intemational co-operation with due respect for national sovereignty o f states. The intemational negotiations on a framework convention should start as quickly as possible after presentation o f this Report in line with Resolution SS II/3 C l i m a t e . C . (August 1990) of the U N E P Governing Council and Resolution 8 ( E C - X L I I , June 1990) of the W M O Executive C o u n c i l . M a n y , essentially d e v e l o p i n g , countries stressed that the negotiations must be conducted in the forum, manner and with the timing to be decided by the U N General Assembly.

m e a s u r e s w h i c h e n h a n c e the c a p a c i t y o f d e v e l o p i n g c o u n t r i e s to d e v e l o p p r o g r a m m e s to address c l i m a t e c h a n g e , i n c l u d i n g research and development activities and p u b l i c awareness and education programmes, such as:

^

+ the development o f the human resources n e c e s s a r y to t a c k l e the p r o b l e m o f c l i m a t e change and its adverse effects: + the p r o v i s i o n o f s t u d y a n d t r a i n i n g programmes in subjects and techniques related to climate change; +

5.0.1 This convention, and any additional protocols that might be agreed upon, w o u l d provide a f i r m basis for effective co-operation to act on greenhouse gas emissions and adapt to any adverse effects o f climate change. The convention should recognize climate change as a c o m m o n concem o f mankind and, at a m i n i m u m , contain general principles and obligations. It should be framed in such a way as to gain the adherence o f the largest possible number and most s u i t a b l y b a l a n c e d range o f c o u n t r i e s w h i l e permitting timely action to be taken.

the provision o f skilled personnel and the

material necessary to organize education programmes to develop locally the skills necessary to assess climate change and combat its adverse effects; +

International co-operation and future work

the development o f climate-related research

programmes organized on a regional basis;

5.0.2 K e y issues for negotiations will include the criteria, t i m i n g , legal form and incidence o f any obligations to control the net emissions o f greenhouse gases, how to address equitably the consequences for all, any institutional mechanisms including research and monitoring that may be required, and in particular, the requests of the developing countries for additional financial resources and for the transfer of technology on a preferential basis. The possible elements o f a framework convention on climate change were identified and discussed by W o r k i n g Group III in its legal measures topic paper, appended to its Policymaker Summary.

f a c i l i t a t i n g the p a r t i c i p a t i o n o f d e v e l o p i n g countries in fora and organizations such as: the Intemational Geosphere-Biosphere Programme, the L a n d - O c e a n Interactions in the Coastal Z o n e , the Biosphere Aspects o f the H y d r o l o g i c a l C y c l e , the G l o b a l Change Impact on Agriculture and Society, the W o r l d C l i m a t e P r o g r a m m e , the M a n and the Biosphere Programme; facilitating participation by developing countries in intemational fora on global climate change such as the I P C C ;

The I P C C recommends that research regarding the science of climate change in general, technological d e v e l o p m e n t a n d the i n t e r n a t i o n a l e c o n o m i c implications, be intensified.

strengthening e x i s t i n g education and research institutions and the d e v e l o p m e n t o f new ones at national and regional levels.

Because climate change would affect, either directly or indirectly, almost every sector o f society, broad global understanding o f the issue w i l l facilitate the adoption and the implementation o f such response o p t i o n s as d e e m e d n e c e s s a r y and a p p r o p r i a t e .

Further efforts to achieve such global understanding are urgently needed.

Further, co-operation and assistance for adaptive measures w o u l d be required, noting that for some r e g i o n s a n d c o u n t r i e s , a d a p t a t i o n r a t h e r than limitation activities are potentially most important.

The I P C C concludes that the recommendations o f the S p e c i a l C o m m i t t e e need not and s h o u l d not a w a i t the o u t c o m e o f future n e g o t i a t i o n s on a climate convenrion. It appeals to the multilateral and bilateral funding organizations to implement its recommendations. It further appeals to govemments for c o n t i n u i n g and increased contributions to the I P C C Trust Fund on an urgent basis.

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IPCC Overview

Method 12

APPENDIX

Scenario A (Business-as-Usual) assumes that few or no steps are taken to limit greenhouse gas emissions. Energy use and clearing of tropical forests continue and fossil fuels, in particular coal, remain the worid's primary energy source.

T h e M o n t r e a l P r o t o c o l comes into effect but without strengthening and with less than 100 percent compliance.

Under this scenario, the equivalent o f a doubling o f preindustrial C O 2 levels occurs, according to W o r k i n g Group I, by around 2025.

Emissions scenarios developed by IPCC T h e I P C C used t w o methods to d e v e l o p scenarios o f future emissions: O n e method used g l o b a l models to d e v e l o p four scenarios which were subsequently used by W o r k i n g Group I to develop scenarios o f future warming. A l l of these four scenarios assumed the same g l o b a l economic growth rates taken from the W o r l d Bank projections and the same population growth estimates taken f r o m the U n i t e d N a t i o n s studies. T h e a n t h r o p o g e n i c e m i s s i o n s o f c a r b o n d i o x i d e and methane from these scenarios are shown in Figures 1 and 2 below.

Scenario В (Low Emissions Scenario) assumes that the energy supply mix of fossil fuels shifts towards natural gas, large efficiency increases are achieved, deforestation is reversed and emissions o f C F C s are reduced by 50% from their 1986 levels. This results in an equivalent doubling o f pre-industrial carbon dioxide by about 2040.

Scenario С (Control Policies Scenario) assumes that a shift towards renewable energies and safe nuclear energy takes

The second method used studies o f the energy and agriculture sectors submitted by over 21 countries and international organizations to estimate C O 2 emissions.

place in the latter part o f the next century, C F C gases are phased out and agricultural emissions (methane and nitrous oxide) are limited; an equivalent doubling o f pre-industrial carbon dioxide w i l l occur in about 2050.

Both scenario approaches indicate that C O 2 emissions w i l l grow from about 7 B t C (billion or 1000 m i l l i o n tonnes carbon) per year now to 12-15 B t C per year by the year 2025. Scenario A (Business-as-Usual) includes a partial phase-out o f C F C s under the Montreal Protocol and lower C O , and CH4 emissions than the Reference Scenario. T h e Reference Scenario developed through country and intemational studies o f the energy and agriculture groups, includes higher C O 2 emissions and assumed a total C F C phase-out. T h e results indicate that the C O 2 equivalent concentrations and their effects on global climate are similar.

Scenario D (Accelerated Policies Scenario) assumes that a rapid shift to renewable energies and safe nuclear energy takes place eariy in the next century, stringent emission controls i n industrial countries and moderate growth o f emissions in developing countries. This scenario, which assumes carbon dioxide emissions are reduced to 5 0 % o f 1985 l e v e l s , s t a b i l i z e s e q u i v a l e n t c a r b o n d i o x i d e concentrations at about twice the pre-industrial levels towards the end o f the next century.

Figure I Projected man-made CO2 emmissions

Figure 2 Projected man-made Methane emmissions

(Billion or 1000 million tonnes carbon per year)

ui Q X

о

(Million tonnes per year) 900

BUSINESS AS-USUAL

шС

20 H

Z а

3 С

H

Sí

О ^ о

800

BUSINESS AS-USUAL

tus

юн

< о г ю

<2

IS

SCENARIO D 1980

2000

2020

2040

2060

2080

1980

210

2000

2020

2040

2060

2080 2 1 0 0

YEAR

YEAR

2 A l l of the scenarios assumed some level of compliance with the Montreal Protocol but not with all of the (June 1990) amendments agreed to in London. The London amendments to the Montreal Protocol, when fully implemented, would result in a virtually complete elimination of production of fully halogenated C F C s , halons, carbon tetrachloride and methyl chloroform early in the 21st century. The Parties of the Protocol also call for later elimination of H C F C s . Thus, the assumptions of Scenarios A and В overestimate the radiative forcing potential of C F C s and halons. Additionally, the U N has provided recent population projections that estimate higher population than used in the global model scenarios (Scenarios A through D); use of these newer projections would increase future CO2 emissions. Additionally, the Reference Scenario CO2 emissions are higher than Scenario A (Business-as-Usual), suggesting Scenario A (Business-as-Usual) may be an underestimate.

61

IPCC Ovei-view

Method 2 (see

footnote 2 on previous page)

U s i n g the second method, the so-called Reference Scenario was developed by the Energy and Industry Subgroup and Agriculture and Forestry Subgroup of W o r k i n g G r o u p III. Under the Reference Scenario, global C O , emissions from all sectors grow from approximately 7.0 B t C (per year) in 1985 to over 15 B t C (per year) m 2 0 2 5 . T h e energy contribution grows from about 5 B t C (per year) to over 12 B t C (per year). Primary energy demand more than doubles between 1985 and 2025 with an average growth rate o f 2.1%. The per capita energy emissions in the industrialized countries increase from 3.1 tonnes carbon ( T C ) in 1985 to 4.7 T C in 2025: for the developmg countries, they rise from 0.4 T C in 1985 to 0.8 T C in 2025.

Summary A l l o f the above scenarios provide a conceptual basis for considering possible future patterns of emissions and the broad responses that might affect those patterns. N o full assessment was made o f the total e c o n o m i c costs and benefits, technological feasibility, or market potential of the underlying policy assumptions. Because of the inherent l i m i t a t i o n s i n o u r a b i l i t y to estimate future rates o f population and economic growth, individual behaviour, technological innovation, and other factors which are crucial for determining emission rates over the course o f the next century, there is some uncertainty in the projections o f greenhouse gas e m i s s i o n s . R e f l e c t i n g these inherent difficulties, the I P C C ' s work on emissions scenarios are the best estimates at this time covering emissions over the next century, but continued work to develop improved assumptions and methods for scenario estimates w i l l be useful to guide the development o f response strategies.

62